In UMTS (Universal Mobile Telecommunications System) networks, attempts are made to adopt HSDPA (High Speed Downlink Packet Access) or HSUPA (High Speed Uplink Packet Access) for the purpose of improving frequency utilization efficiency and improving a data rate to thereby make the most of features of W-CDMA (Wideband Code Division Multiple Access)-based systems. Regarding this UMTS network, Long Term Evolution (LTE) is being studied aiming at a higher data rate and lower delay or the like.
Third-generation systems can generally realize a transmission rate of a maximum of the order of 2 Mbps on a downlink using a fixed band of 5 MHz. On the other hand, LTE-based systems can realize a transmission rate of a maximum of the order of 300 Mbps on a downlink and the order of 75 Mbps on an uplink using a variable band of 1.4 MHz to 20 MHz. Furthermore, in the UMTS networks, a system as the successor to LTE is also being studied for the purpose of achieving a wider band and higher rate (e.g., LTE Advanced (LTE-A)). For example, in LTE-A, 20 MHz which is the maximum system band of the LTE specification is scheduled to be extended to the order of 100 MHz. Furthermore, In LTE-A, the maximum number (four) of transmission antennas in the LTE specification is scheduled to be increased to eight.
Furthermore, in the LTE-based system, a MIMO (Multi Input Multi Output) system is being proposed as a radio communication technique for transmitting/receiving data using a plurality of antennas and improving a data rate (frequency utilization efficiency) (e.g., see Non-Patent Literature 1). In the MIMO system, a transmitter/receiver is provided with a plurality of transmitting/receiving antennas and different transmission information sequences are simultaneously transmitted from different transmitting antennas. On the other hand, the receiver side separates and detects information sequences which are simultaneously transmitted taking advantage of the fact that different fading fluctuations are generated between the transmitting/receiving antennas, and can thereby increase the data rate (frequency utilization efficiency).